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In this episode of Wrong, But Useful, we are joined by freelance mathematician @becky_k_warren, formerly of NRICH

- Becky likes sharing maths with people who "don't like maths" and the #beingmathematical twitter chat
**Number of the podcast**: 157, which is the middle of a sexy prime triplet. Colin goes all Rees-Mogg for a moment.
- The Aperiodical Math-off is reaching its final stages. We were rooting for @ajk_44. Dave suggests a televised version. Colin dislikes the tournament format.
- @cmonmattthink has More Questions Than Answers
- @cuttheknotmath (Alexander Bogomolny in real life) has died.
- The University of Waterloo now has an elliptical pool table. Here's a simulator.
- Becky loves Islamic patterns, including the work of @Samira_Mian (her instagram is here and her website here). Becky also recommends the iOrnament app.
- Dave is teaching the Core Maths qualification in the coming year, including Fermi estimation questions.
- Colin gabbles about arctangent identities like $\arctan\br{\frac{1}{8}} = \arctan\br{\frac{1}{13}} + \arctan \br{\frac{1}{21}}$.
- Adam tells us about an Italian jackpot that rolled over 200 times and the possibility of the National Lottery being bankrupted by guaranteed &gbp;10 prizes. We discuss scratchcards, despite knowing little.
**Puzzle feedback**: from episode 56, @chrishazell gets a belated gold star for tweeting "required numbers take the form 3999...97 (any number of 9s including none). That form is sufficient because $2\times(4\times10^n - 3) - 1=8\times 10^n - 7$, proof that it's necessary is long winded and not very instructive!". From episode 57, gold stars to @samhartburn and @chrishazell for finding a depth below the surface of 8 inches.
**This month's puzzle**: the grass in a meadow is enough to feed 20 cows for 30 days or 30 cows for 15 days. Assuming the grass grows at a constant rate, for how long can the grass support 40 cows? How many cows could it support indefinitely?

Speak with you, loyal listeners, next month.

* Edited 2018-07-16 to replace hissy audio.

* Edited 2018-07-21 to correct spelling of Bogomolny.

## Colin

Colin is a Weymouth maths tutor, author of several Maths For Dummies books and A-level maths guides. He started Flying Colours Maths in 2008.
He lives with an espresso pot and nothing to prove.